/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect.testing.features;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.Helpers;

import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.SortedSet;

/**
 * Optional features of classes derived from {@code Collection}.
 *
 * @author George van den Driessche
 */
// Enum values use constructors with generic varargs.
@SuppressWarnings("unchecked")
@GwtCompatible
public enum CollectionFeature implements Feature<Collection>
{
    /**
     * The collection must not throw {@code NullPointerException} on calls such as {@code
     * contains(null)} or {@code remove(null)}, but instead must return a simple {@code false}.
     */
    ALLOWS_NULL_QUERIES,
    ALLOWS_NULL_VALUES(ALLOWS_NULL_QUERIES),

    /**
     * Indicates that a collection disallows certain elements (other than {@code null}, whose validity
     * as an element is indicated by the presence or absence of {@link #ALLOWS_NULL_VALUES}). From the
     * documentation for {@link Collection}:
     *
     * <blockquote>
     * <p>
     * "Some collection implementations have restrictions on the elements that they may contain. For
     * example, some implementations prohibit null elements, and some have restrictions on the types
     * of their elements."
     *
     * </blockquote>
     */
    RESTRICTS_ELEMENTS,

    /**
     * Indicates that a collection has a well-defined ordering of its elements. The ordering may
     * depend on the element values, such as a {@link SortedSet}, or on the insertion ordering, such
     * as a {@link LinkedHashSet}. All list tests and sorted-collection tests automatically specify
     * this feature.
     */
    KNOWN_ORDER,

    /**
     * Indicates that a collection has a different {@link Object#toString} representation than most
     * collections. If not specified, the collection tests will examine the value returned by {@link
     * Object#toString}.
     */
    NON_STANDARD_TOSTRING,

    /**
     * Indicates that the constructor or factory method of a collection, usually an immutable set,
     * throws an {@link IllegalArgumentException} when presented with duplicate elements instead of
     * collapsing them to a single element or including duplicate instances in the collection.
     */
    REJECTS_DUPLICATES_AT_CREATION,

    SUPPORTS_ADD,
    SUPPORTS_REMOVE,
    SUPPORTS_ITERATOR_REMOVE,
    FAILS_FAST_ON_CONCURRENT_MODIFICATION,

    /**
     * Features supported by general-purpose collections - everything but {@link #RESTRICTS_ELEMENTS}.
     *
     * @see java.util.Collection the definition of general-purpose collections.
     */
    GENERAL_PURPOSE(SUPPORTS_ADD, SUPPORTS_REMOVE, SUPPORTS_ITERATOR_REMOVE),

    /**
     * Features supported by collections where only removal is allowed.
     */
    REMOVE_OPERATIONS(SUPPORTS_REMOVE, SUPPORTS_ITERATOR_REMOVE),

    SERIALIZABLE,
    SERIALIZABLE_INCLUDING_VIEWS(SERIALIZABLE),

    SUBSET_VIEW,
    DESCENDING_VIEW,

    /**
     * For documenting collections that support no optional features, such as {@link
     * java.util.Collections#emptySet}
     */
    NONE;

    private final Set<Feature<? super Collection>> implied;

    CollectionFeature(Feature<? super Collection>... implied)
    {
        this.implied = Helpers.copyToSet(implied);
    }

    @Override
    public Set<Feature<? super Collection>> getImpliedFeatures()
    {
        return implied;
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Inherited
    @TesterAnnotation
    public @interface Require
    {
        CollectionFeature[] value() default {};

        CollectionFeature[] absent() default {};
    }
}
